Generally, helmets are worn to protect a head of a rider when the rider rides a motorcycle or the like, and it is provided that helmets be worn for safety when driving.
Helmets have a sufficient strength capable of withstanding impact applied from the outside without being damaged and thus serve to protect the head of a wearer, and absorb and mitigate the impact and thus serve to promote safety of the wearer.
Such helmets may be classified into a half face type, an open face type, a full face type, and the like in accordance with forms thereof.
The half face type helmet is formed to cover only an upper part of the head of a user, and has a characteristic that it is easy to carry due to a small volume, and is highly preferred by users due to being convenient to wear.
The open face type helmet is formed to cover an upper part of the head of the user and a side part and a rear part of a lower part of the head, and has the characteristic of a wide protective region in comparison to the half face type helmet.
The full face type helmet is formed to cover an entire region of the head of the user including the user's face, and has the characteristic of being somewhat inconvenient to wear in comparison to the half face type helmet and the open face type helmet despite having the widest protective region in comparison to the half face type helmet and the open face type helmet.
The above-described various forms of helmets are selectively used depending on timing and purpose in many cases, and, depending on users, all of the helmets are purchased and used in many cases.
However, in a conventional case, the user has to separately purchase all types of helmets described above to wear different helmets depending on purpose, which leads to problems of imposing a cost burden on the user and being difficult for the user to store the helmets.
Therefore, a method of solving such problems is required.